Positive electrode material, manufacturing method thereof, positive electrode for non-aqueous rechargeable battery, and non-aqueous rechargeable battery

Abstract

A positive electrode material that can form a positive electrode mixture containing composition with reduced changes over time and high productivity, a manufacturing method thereof, a non-aqueous rechargeable battery less likely to swell and having a high storage characteristic during storage at high temperatures, and a positive electrode that can form the battery are provided. The object is solved by providing a positive electrode material having a coating layer of an organic silane compound on a surface of a positive electrode active material made of a lithium nickel composite oxide represented by the general compositional formula (1): Li_1+xMO₂ where −0.5≦x≦0.5, M represents a group of at least two elements including at least one of Mn and Co and Ni, and 20≦a≦100 and 50≦a+b+c≦100 when the ratios (mol %) of Ni, Mn, and Co in the elements forming M are a, b, and c, respectively.

Description

TECHNICAL FIELD[0001]The present invention relates to a positive electrode material for use in a non-aqueous rechargeable battery, a manufacturing method thereof, a positive electrode for a non-aqueous rechargeable battery, and a non-aqueous rechargeable battery.BACKGROUND ART[0002]In recent years, there has been a sharply increasing demand for high energy density, non-aqueous rechargeable batteries as portable electronic equipment such as cell phones and note type personal computers have developed and electric automobiles have become commercially available. Today, non-aqueous rechargeable batteries that could satisfy the demand use a wide variety of positive electrode active materials including lithium cobalt oxides such as lithium cobaltate (LiCoO2), lithium nickel composite oxides such as lithium nickelate (LiNiO2) and lithium manganese composite oxides such as lithium manganite (LiMn2O4).[0003]Among the above, lithium nickelate having a greater discharge capacity than lithium co...

AI Technical Summary

Benefits of technology

[0057]In the positive electrode according to the first embodiment of the present invention, a positive electrode mixture layer is formed by the step of forming a composition (a positive electrode mixture containing composition) that includes a positive electrode active material including the lithium nickel composite oxide, an organic silane compound, and a binder, applying the composition on one or both surfaces of a collector, and drying it. In the composition described above, a surface of the positive electrode active material would be coated with the organic silane compound, which can significantly reduce moisture in the air or composition to adsorb to the positive electrode active material. As a result, an alkaline component can be restrained from newly forming based on a reaction between the positive electrode active material and the moisture, so that swelling of a non-aqueous rechargeable battery during storage at high temperatures attributable to the alkaline component and the capacity drop can be reduced.

[0058]The positive electrode material according to the present invention includes a positive electrode active material having a coating layer of an organic compound formed on a surface of the positive electrode active material (the method of forming the coating layer of the organic compound will be described later), the organic compound (such as an organic silane compound) would be dispersed in the positive electrode mixture containing composition in addition to coating the positive electrode active material, and the organic compound (such as an organic silane compound) moves to the interface between the positive electrode mixture containing composition and the air and serves like a coating, so that moisture in the air may not easily come into the positive electrode mixture containing composition. Therefore, the amount of moisture adhered to the positive electrode active material in the positive electrode mixture containing composition is reduced. Also when fluorine based resin such as PVDF is used for the binder, de-fluorination in which fluorine as a constituent element desorbs in the form of hydrofluoric acid could be reduced and gelation of the positive electrode mixture containing composition could be reduced. This improves the stability of the positive electrode mixture containing composition and the long term storage characteristic improves, so that the rejection rate is reduced, and therefore the productivity of a positive electrode and hence the productivity of a non-aqueous rechargeable battery using the same can be improved.

[0059]Examples of the organic compound that forms the coating layer include an organic silane compound, an organic titanium compound, an organic palladium compound, an organic magnesium compound, an organic lithium compound, an organic aluminum compound, a

Problems solved by technology

However, lithium nickelate has a less stable crystal structure than that of lithium cobaltate in a charged state and cannot be used to make sufficiently safe batteries as it is.

In addition, as for a charge/discharge cycle life, the batteries produced using lithium nickelate do not provide satisfactory properties because of the low reversibility of the crystal structure of lithium nickelate.

However, when a positive electrode mixture that contains the lithium nickel composite oxide described above, a conduction aid, and a binder is dispersed in a solvent and prepared into a slurry or paste type positive electrode mixture containing composition, and the composition is applied on one or both surfaces of a collector made of a metal foil, followed by drying to form a positive electrode mixture layer, gela

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